Black Belt Sudoku

At home, while commuting, during lunch hours…people around the world are eagerly working on Sudoku puzzles whenever and wherever they can!

Created in the United States, these intriguing conundrums were originally called Number Place puzzles. Their recent rise in popularity began in Japan, where the name translated as sudoku. Here we’ve indicated the skill level necessary to complete each sudoku book in this series in the same way Japanese karate levels are ranked: by different colored belts...